In this tutorial we’ll cover the following topics:

Basic Maps

There is no function for displaying maps in the base R functionality. To display a simple map, we use the ‘maps’ package.

library(maps)

For our examples we will be using Indiana air monitoring site locations.

monitors <- read.table(header=T, text='
  monitorid        lat        long   datum                    name            
          1   41.60668  -87.304729   WGS84              Gary-IITRI
          2  39.811097  -86.114469   WGS84  Indpls-Washington-Park
          3  39.749019  -86.186314   WGS84      Indpls-Harding-St.
          4  38.013248  -87.577856   WGS84  Evansville-Buena-Vista
          5  39.159383  -86.504762   WGS84             Bloomington
                       ')

First, let’s create a simple Indiana map.

map(database = 'state', regions = 'indiana')

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Now we can use our monitor lats and longs to add points to the map using the base points() function.

points(x = monitors$long, y = monitors$lat)

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We can jazz it up a bit by making it a county map and changing the symbol type and color.

map(database = 'county', regions = 'indiana')
points(x = monitors$long, y = monitors$lat, pch = 19, col = 'red')

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Google Maps

To make interactive Google maps, we can use the googleVis package.

library(googleVis)

We have to do some formatting first. The coordinates must be in the form lat:long so we need to create a data frame with a variable in that format.

google.location <- paste(monitors$lat, monitors$long, sep = ":")
monitors.google <- data.frame(monitors, google.location)
g.inter.map <- gvisMap(data = monitors.google, locationvar = "google.location",
                       tipvar = "name")
plot(g.inter.map)

Leaflet Maps

Leaflet is another interactive map that can be created in R using the leafletR package.

library(leafletR)

The coordinates must first be converted to a GeoJSON file using the toGeoJSON() function.

leaf.data <- toGeoJSON(data = monitors[, -1], dest = tempdir(), name = "monitors")

And we create the map using the leaflet() function.

leaf.map <- leaflet(data = leaf.data, popup = "name", dest = tempdir())
browseURL(leaf.map)

leaflet

R Markdown

This tutorial was created using RStudio’s R Markdown. The code can be found on GitHub.